Steering Reaction Force Control at Engine Stop Position

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Solution Overview

Problem

Steer-by-wire vehicle steering systems can cause discomfort to drivers when the engine is stopped, as the steering wheel may rotate in unintended directions or apply unintended reaction forces, especially when getting on or off the vehicle.

Innovation Solution

A vehicle steering system with a reaction force actuator that applies a controlled reaction force to the steering member based on its stopped time position, adjusting the force according to displacement and switching control maps based on the engine's state to minimize unintended movements and forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If control is executed to make wheel turning angle coincide with steering wheel rotational position when engine is stopped, then steering responsiveness is improved, but the steering wheel may rotate in unintended directions or apply unintended reaction forces causing driver discomfort

Engineering Contradiction:

Improvesteering responsivenessVSAvoiddriver discomfort

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The control map parameters are dynamically changed based on engine state. When the engine is stopped, the control map is switched to a second control map with different reaction force characteristics compared to the first control map used when the engine is operating. This parameter change allows the system to maintain steering responsiveness while preventing unintended rotation and reaction forces that cause driver discomfort.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The reaction force actuator dynamically adjusts its control strategy based on the engine's operational state. The ECU monitors engine status and switches between different control maps in real-time, making the steering system adaptive to different operating conditions. This dynamic adjustment ensures appropriate reaction forces are applied whether the engine is running or stopped, preventing driver discomfort while maintaining responsiveness.

Inventive Principle:

Principle #15Dynamics

2Reliability

If reaction force actuator applies reaction force based on stopped time position when driving source is stopped, then unintended steering movements are prevented, but power consumption increases

Engineering Contradiction:

Improvesteering stabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The reaction force actuator operates periodically rather than continuously when the driving source is stopped. The ECU controls the actuator to apply reaction forces at specific intervals or under specific conditions (such as when displacement exceeds certain thresholds), rather than maintaining constant operation. This periodic action maintains steering stability while significantly reducing overall power consumption during engine stop periods.

Inventive Principle:

Principle #19Periodic action

3Use of energy by moving object

If maximum reaction force is reduced when driving source is stopped, then power consumption is suppressed, but steering control authority is reduced

Engineering Contradiction:

Improvepower consumptionVSAvoidsteering control authority

Core Design Contradiction:

Use of energy by moving objectVSForce

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Prevents uncomfortable steering experiences by maintaining intended steering positions and forces, reducing power consumption, and optimizing power usage during engine stops and starts.

Implementation Method 1

the reaction force actuator is configured to apply the reaction force to the steering member based on a stopped time position that is a position of the steering member at a time when the driving source is stopped

Methodology Applied

Scientific EffectSpring force: Spring

Data Source

PatentUS12473011B2Vehicle steering system

Publication Date: 2025.11.18 HONDA MOTOR CO LTD

AI summary

To prevent a driver from feeling uncomfortable when the driver touches a steering member in a state where a driving source is stopped, a vehicle steering system (1) is provided in a vehicle (2) that travels by a driving force generated by a driving source (51). The vehicle steering system (1) includes; a steering member (10) configured to accept a steering operation; and a reaction force actuator (13) configured to apply a reaction force to the steering member (10) in response to the steering operation. In a state where the driving source (51) is stopped, the reaction force actuator (13) is configured to apply the reaction force to the steering member (10) based on a stopped time position that is a position of the steering member (10) at a time when the driving source (51) is stopped.